The invention relates to a lifting hook comprising a hook body with a hook stem and a hook tip; a safety latch with a fastening end and a free latch end, the fastening end of the latch being pivotally fastened close to the hook stem to be moved between an open and a closed position, the safety latch being in its open position substantially against an inner side of the hook body in a position that leaves the hook jaw free while in the closed position of the safety latch the latch end extends across the hook jaw to the tip of the hook and against it, the latch end resting against the inside of the hook body and its jaw, closing the jaw; and actuating means of the safety latch arranged between the safety latch and the hook body. The invention also relates separately to a safety latch to be attached to existing hooks, in which case the safety latch is of the above-described type.
A safety latch of a lifting hook is meant to assist the user of a lifting hook of a crane in safe and efficient loading and unloading of the hook. The loading of the hook naturally refers to fastening a load to the hook and the Unloading, correspondingly, to releasing the load from the hook. Safety and efficiency are significantly increased if the user is able to use both hands at the same time for releasing the load.
In prior art hooks, the safety latch is typically pressed open against a spring force that pushes the safety latch to close it, and kept in the open position by one hand. This prevents the hand from being used for releasing the load as the hand must be used for keeping the safety latch open all the time when the load is being released. Moreover, opening the safety latch of big hooks and keeping it open requires a lot of force. Hence the load is very difficult to release and often another person is needed to keep the safety latch open. There is also a risk of hands or fingers getting caught between the safety latch and the hook body. All of these aspects together may lead to a temptation to ignore the use of the safety latch, for example by tying it permanently to an open position against the inner side of the hook body by taping, for example.
However, methods have been developed for keeping the safety latch open without the user needing to use his/her hands for it. For example, the safety latch may be provided with a kind of an operating handle attached by articulation to the safety latch, at a distance from its fastening end, the handle extending around the hook body and being lockable behind the hook body to a position that keeps the safety latch open. An example of such a safety latch is disclosed in U.S. Pat. No. 3,008,210. In this solution, however, the handle has to be separately released after the load has been detached in order to tension the safety latch again to the closed position. The releasing may require even quite a lot of strength, and if the safety latch has a strong spring, the user may still hurt his/her hands if they for some reason get caught between the operating handle and the hook body or between the latch end of the safety latch and the hook body. Then again, if the safety latch is left or forgotten completely open after a load has been fastened and for the duration of a subsequent lifting, the safety latch is of no use.